1. Field
Embodiments described herein relate generally to a lifting device having a floor movable relative to a base structure. More specifically, embodiments described herein relate to a drilling rig floor vertically movable relative to a base structure.
2. Description of the Related Art
Conventional drilling rigs, such as land based drilling rigs, typically include a mast structure supported by a substructure having a base and a drilling floor. When the drilling rig is set-up on a location, the drilling floor typically needs to be spaced away from the base structure, for example raised relative to the base structure to provide space for equipment, such as valves, fittings, blowout preventers, and other necessary equipment, between the base structure and the drilling floor.
In some conventional drilling rigs, the drilling floor is coupled and raised relative to the base structure in a general pivoting or cantilevered fashion such that the drilling floor is raised in an arc relative to the base. Raising the drilling floor relative to the base structure in this manner requires sequential lifting steps as lift devices, such as hydraulic cylinders, are coupled and decoupled repeatedly to the drilling floor to gain an enhanced mechanical advantage and/or to remain within the working range of the hydraulic cylinder. As such, numerous workers are required to be in the area between the drilling floor and base structure during erection, which poses a safety issue. This method also takes considerable time, requires substantial land area for set-up and lifting (or lowering), requires permitted hauls to and from the site, and requires a substantial amount of hydraulic equipment for operation.
Solutions to the challenges of safety and reducing the drilling rig footprint, physically and environmentally, have been attempted but have not proven to be workable or commercially desirable. Thus, there remains a need for a drilling rig having a movable drill floor that occupies a smaller footprint during raising or lowering, requires less time and personnel for operation, and minimizes the use of hydraulic equipment.